This invention relates to reciprocable devices, and more particularly to a reciprocable device having an improved valving system for ensuring dependable switching of the reciprocable member travel direction during operation.
Reciprocable devices typically include a reciprocable member which reciprocates to perform a useful function, such as pumping a flowable material, compressing a gas, metering a fluid or providing a reciprocating output for other purposes. A driving fluid under pressure, which may be either a liquid or a gas, is commonly used to reciprocate the reciprocable member. For example, the reciprocable member may be a piston having first and second faces which are alternately exposable to driving fluid under pressure and to exhaust.
A valve or valving system is provided for controlling the exposure of the piston faces to the pressurized driving fluid and to exhaust. In order for the valve system to perform its function, it typically includes one or more valve elements which must be moved periodically from one position to another to bring about reciprocation of the piston. Movement of the reciprocable member can be used to control movement of the valve elements.
Reciprocating devices of the type described are shown, for example, in U.S. Pat. No. 4,610,192 to Hartley et al. The construction disclosed therein employs a bistable toggle mechanism which is driven just over center by energy from the piston and then driven by stored spring energy. The toggle action reverses the pressure and exhaust valves to bring about a reversal of movement of the reciprocable member. The valves in this prior art system are fluid pressure biased.